OFDMA_Part6 - wireless channel. s [ n ] consists of a...

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6 802.11a/g/n standards. Now that we know how OFDM evolved, let us move onto the theory behind OFDM. The concepts and equations regarding the theory of OFDM have been adapted from the textbook titled Wireless Communications by Andrea Goldsmith [15]. The following sub-sections first discuss the basics of OFDM. After that, the multiple-access version of OFDM, i.e. OFDMA, has been presented. 2.1 Basics of OFDM To understand the basics of OFDM, consider the OFDM transmitter (TX) shown in Figure 2 and the OFDM receiver (RX) shown in Figure 3. s [ n ] is the message to be sent from TX to RX over a
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Unformatted text preview: wireless channel. s [ n ] consists of a sequence of bits. At any OFDM symbol time T s , the sequence of bits is mapped as N frequency-domain symbols { X , X 1 ,, X N-2 , X N-1 } as shown in Figure 2. OFDM Transmitter Figure 2. The baseband modulation used for each of the N symbols could be different; as an example, 4-QAM has been used for each symbol in Figure 2. The N frequency-domain symbols { X , X 1 ,, X N-2 , X N-1 } are then passed through the FFT-1 block to get N time-domain symbols...
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